Major revamp.

nixos/overlays/detjson.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Deterministic layer json: https://github.com/docker/hub-feedback/issues/488
+
+import sys
+reload(sys)
+sys.setdefaultencoding('UTF8')
+import json
+
+# If any of the keys below are equal to a certain value
+# then we can delete it because it's the default value
+SAFEDELS = {
+    "Size": 0,
+    "config": {
+        "ExposedPorts": None,
+        "MacAddress": "",
+        "NetworkDisabled": False,
+        "PortSpecs": None,
+        "VolumeDriver": ""
+    }
+}
+SAFEDELS["container_config"] = SAFEDELS["config"]
+
+def makedet(j, safedels):
+    for k,v in safedels.items():
+        if k not in j:
+            continue
+        if type(v) == dict:
+            makedet(j[k], v)
+        elif j[k] == v:
+            del j[k]
+
+def main():
+    j = json.load(sys.stdin)
+    makedet(j, SAFEDELS)
+    json.dump(j, sys.stdout, sort_keys=True)
+
+if __name__ == '__main__':
+    main()